There's way too many feminist issues to talk about but regarding monsters there's a few ideas I have.
One focus of feminism revolves around sex positivity and making comprehensive sex education available in schools. Birth control, stds, consent, gender identity, healthy ways to deal with sexuality and sexual desires in ways that let kids feel comfortable with sex. As we understand monster girls, ths could mean an agreement between the two groups.
I think the biggest source of friction would be the way many monsters rape men. As far as I understand it, monster girls make rape enjoyable, even if it's something that was initially unwanted. Human rape can be frightening, painful, and traumatic. If monsters heard about human rape, they might not understand how different it is. They would also likely struggle to understand the ways many women find attention from random men to be intimidating or unwanted. But they could learn.
Men who commit rape, or other forms of sexual harassment are an issue for men to solve themselves, by addressing it and holding other men accountable. I'd like to think a lot of the creepier men would lay off with how many women are suddenly stronger and scarier than them but there's plenty of more submissive or less outgoing monsters that they could turn their focus to. Feminists would likely adapt to the fact that many monsters find themselves the target of unwanted advances. Monsters have standards too. And I'm not concinved that there's a 0% rate of trauma from men being raped by monsters.
One of the wildest assertions by KC is that all monster girls are straight. Like sure he can say whatever he wants in his own world but if they were real, there would be gay monster girls who'd have a lot of trouble avaoiding harassment by men. They would likely find support in feminism.
Too long. But it's easy to misunderstand many of the issues feminism deals with. And of course there's many feminists with different attitudes or ideas, like any movement. It's easy to find examples of women who make the movement look bad. But many feminists are rational people with perfectly legitimate reasons. Feminists don't hate submissive women, but they might hate that a woman was made to act meek and quiet due to abuse or mistreatment by men. Monster girls are supernaturally predisposed to loving men, feminists are humans who see that men are responsible for a lot of problems. It's easy for monsters to think whatever they want of men because they are categorically stronger than men.